The present invention relates to a plasma etching system, and in further detail, it relates to a dry etching system in which the etching rate and the variation in surface roughness of quartz glass members are reduced, and in which the generation of particles during etching is minimized.
Recently, a dry etching process employing gas plasma has been used in the etching treatment of the surface of a semiconductor device such as a silicon wafer, etc. In the dry etching process, a gas is introduced into a naturally occurring quartz glass vessel and excited by a microwave to generate a plasma therein. The gas thus excited is then used in the fine patterning process by etching the oxide films and the Poly-Si films provided on the surface of a silicon wafer. In the dry etching process, though a gas containing fluorine such as CF4, etc. is used, it has a disadvantage because the gas containing fluorine forms a by-product such as HF, etc. in a plasma state, and the by-product etches quartz glass to generate particles, which adhere on the surface of a semiconductor device such as a silicon wafer thereby impairing the electrical characteristics, especially the dielectric breakdown characteristics. To overcome this disadvantage, materials having excellent resistance against plasma, such as a ceramic vessel, have been developed, but those materials were found to have a higher dielectric constant as compared with quartz glass, and were thereby disadvantageous in that they had poor transmittance of microwaves. Thus, a naturally occurring quartz glass member is still used at present.
In the light of these circumstances, studies have been conducted on the fluorine plasma characteristics of quartz glass; and as a result, it has found that a synthetic quartz glass, as compared with a naturally occurring quartz glass, has excellent fluorine plasma characteristics and a low etching rate and also has a small variation in surface roughness on the surface of the quartz glass, and the generation of particles is suppressed.
Therefore, it is an object of the invention to provide a quartz glass member for use in dry etching which minimizes the generation of particles during an etching process.
A further object of the invention is to provide a dry etching system equipped with the quartz glass member for use in dry etching.
These objects and other objects of the invention which will become apparent from the following specification are provided by a quartz glass member for use in dry etching, wherein at least the inner surface of the member to be brought into contact with plasma is constructed of synthetic quartz glass.
As described above, in the quartz glass member for use in dry etching according to the invention, at least the inner surface of the member to be brought into contact with plasma is constructed of a synthetic quartz glass, and particularly, the synthetic quartz glass constituting the inner surface of the member preferably has a plasma etching rate of 40 nm/min or less and a variation in surface roughness (Rmax) of 1 nm/min or less. If the plasma etching rate of the quartz glass member exceeds 40 nm/min, the particles produced by etching of quartz glass adhere to the surface of the silicon wafer to degrade the electrical characteristics thereof. If the variation in surface roughness (Rmax) of the quartz glass member exceeds 1 nm/min, the surface area of the quartz glass surface in contact with the plasma greatly changes to destabilize the etching rate of the silicon wafer. When the surface of the quartz glass is roughened, the ions and radicals generated by plasma tend to react easily with the surface of the quartz glass and the amount of ions and radicals decreases in the plasma. Moreover, the by-products that are produced by etching are more likely to adhere to the surface of the quartz glass and absorb the ions and radicals. These are the cause for the instability in etching rate. On the other hand, if the surface of the quartz glass member does not undergo etching at all, the by-products that are produced by etching tend to undergo peeling off even if they adhere to the surface of the quartz glass member, and the by-products thus peeled off adhere to the surface of the silicon wafers, resulting in degradation of the characteristics of the silicon wafer. Accordingly, at least, the variation in surface roughness of the quartz glass member is required to be at least 0.001 nm/min. The etching rate of the quartz glass depends on temperature, and the etching rate in the invention is defined to be that at 100xc2x0 C. For instance, an etching rate of 40 nm/min at 100xc2x0 results at 300xc2x0 C. to an etching rate of approximately 700 nm/min.